An automatic transmission mounted on a vehicle, such as an automobile, typically includes a transmission mechanism including: a plurality of planetary gear sets (planetary gear mechanisms); and a plurality of friction engaging elements, such as a clutch device and a brake device. The automatic transmission is configured such that by selectively engaging the friction engaging elements, power transmission paths passing through the planetary gear sets are switched, and as a result, a predetermined gear stage corresponding to a driving state of the vehicle is realized.
In recent years, for the purpose of improving fuel efficiency of the vehicle and the like, an increase in the number of gear stages in the automatic transmission has been advanced, and in accordance with this, the number of planetary gear sets constituting the transmission mechanism tends to increase. However, when the number of planetary gear sets increases, an axial size of the entire automatic transmission increases, and this causes a problem regarding mountability to a vehicle. Especially in a transversely mounted type automatic transmission having a center axis extending in a vehicle body width direction, an interference of the automatic transmission with a frame member of a vehicle body or the like tends to be a problem, so that the problem regarding the mountability to the vehicle may become more significant.
Here, for example, PTL 1 discloses an automatic transmission in which two planetary gear sets constituting the transmission mechanism are arranged so as to overlap each other when viewed from a radial direction. According to this, the axial size of the entire automatic transmission can be made smaller than the axial size of an automatic transmission in which two planetary gear sets are arranged so as to be lined up in an axial direction.
Further, PTL 1 discloses an automatic transmission in which: one planetary gear set is adjacently arranged at one axial side of the two planetary gear sets arranged so as to overlap each other when viewed from the radial direction; and a brake device is arranged at an outer periphery side of the one planetary gear set.